decomp: say the FIX, not the diagnosis

The 64-bit failure now reported Hex-Rays verbatim — "only 64-bit functions can
be decompiled in the current database" — with the actionable half appended after
it. A status bar cuts off the end, so the user got a perfect description of their
problem and nothing about what to do, which is the same dead end as before with
extra words.

  before: sub_0: cannot decompile — only 64-bit functions can be decompiled in
          the current database — Ctrl+L and pick arm:ARMv7-A      (125 chars)
  after:  sub_0: cannot decompile — this database is 64-bit — Ctrl+L, pick
          arm:ARMv7-A                                              (76 chars)

For this one failure the instruction IS the whole message: it can't be fixed in
place (bitness is decided at load), so describing the database serves nobody.
Other Hex-Rays reasons still pass through verbatim — they're usually about the
function, and there the description is the useful part.

Verified the whole path in a live pane on experiments/fibonacci.bin: the load
dialog now shows arm vs arm:ARMv7-A/M/v6-M/v5TE with their bitness spelled out,
picking arm:ARMv7-A gives 54 functions, and sub_0 decompiles:

  void __fastcall __noreturn sub_0(int a1) { ... v2 = sub_E3C(a1, 0); ... }

tests: thumb (16) now asserts the message names the fix rather than quoting
Hex-Rays, and that it fits under 110 chars — the truncation is what made the
last version useless, so it's worth a check. 209/0 scenarios, 30/0 blob.

1 files changed, 8 insertions, 2 deletions

diff --git a/idatui/domain.py b/idatui/domain.py
index a92ea49..084312a 100644
--- a/idatui/domain.py
+++ b/idatui/domain.py
@@ -1383,8 +1383,14 @@ class Program:
             return ""
         reason = str(r.get("reason") or "")
         if reason and r.get("bitness") == 64 and "64-bit" in reason:
-            # Unfixable in place: the database's bitness is decided at load.
-            reason += " \u2014 Ctrl+L and pick arm:ARMv7-A"
+            # Say the FIX, not the diagnosis. Hex-Rays' own sentence ("only
+            # 64-bit functions can be decompiled in the current database") is
+            # accurate and useless: it describes the database, not what to do,
+            # and it's long enough that a status bar cuts off the end — which is
+            # exactly where an appended hint would live. This is unfixable in
+            # place (bitness is decided at load), so the whole message is the
+            # instruction.
+            return "this database is 64-bit \u2014 Ctrl+L, pick arm:ARMv7-A"
         return reason
 
     def set_thumb(self, ea: int, mode: str = "toggle") -> dict: